code: def test_properties():
      """Tests that elbow and knee can be used interchangeably."""
      kn = KneeLocator(
          x,
          y_concave_inc,
          curve_nature="concave",
          curve_direction="increasing",
      )
      assert kn.knee == kn.elbow
      assert kn.norm_knee == kn.norm_elbow
      # pytest compares all elements in each list.
      assert kn.all_knees == kn.all_elbows
      assert kn.all_norm_knees == kn.all_norm_elbows
  
file_path: yellowbrick/tests/test_utils/test_kneed.py
imports: import pytest
  import matplotlib.pyplot
  import numpy
  from yellowbrick.utils.kneed import KneeLocator
label_desc: Use image node_id 11 for calling a global function with example usage: test_properties() without return types